Field of the Invention
The present invention relates to a press-through pack package comprising a covering material film, that can be suitably used primarily for packaging of pharmaceuticals such as tablets or capsules, or foods such as candy or chocolate.
Related Background Art
One known form for packaging of pharmaceuticals and foods is a press-through pack (hereunder, “PTP”) package that comprises a base material and a covering material. PTP packages are formed by preparing a base material molded to have a pocket-shaped recess by vacuum forming or pressure forming of a plastic sheet made of a polyvinyl chloride-based resin or polypropylene-based resin, packing contents into the recess, and then sealing flange sections that are separate from the recess, with a heat sealable covering material.
A PTP package has a construction such that force is applied to the housed contents from the outer side of the base material in the direction of the covering material to tear the covering material, and remove the contents. Therefore, the covering material of the PTP package must have a property of easily tearing when the contents are pushed out (a press-through property). Aluminum foil is currently in wide use as a covering material because of its excellent press-through property.
However, PTP packages employing aluminum foil covering materials are associated with the following problems. Specifically, when the package is discarded after removing the contents, the aluminum foil covering material is preferably separated from the plastic base material from the viewpoint of recent recycling use of resources, but this requires considerable effort and is physically difficult to accomplish. With thermal disposal as well, the large heat value of aluminum foil results in damage to incinerators and melted integration, thereby lowering the incineration efficiency. In addition, production of aluminum requires a large amount of electrical energy, and is associated with problems of cost as well as environmental pollution including CO2 waste. At locations of PTP packaging, almost all detachment of packagers for aluminum foil covering material rolls is carried out by hand, and this increases the burden on workers by handling of heavy items and increases the risk of injury by dropping.
In light of this condition, there have been proposed various types of plastic covering material films as PTP covering materials that do not use aluminum foil (see Patent documents 1-4).
Patent Document 1 describes a PTP covering material sheet comprising 5-250 parts by weight of an inorganic filler with respect to 100 parts by weight of a resin such as a polyolefin, polyester, polyvinyl chloride, polystyrene or styrene copolymer, in order to lower the rupture strength of the resin film and exhibit a satisfactory press-through property.
Patent Document 2 describes a PTP covering material having a resin film layer formed on one side of a polypropylene-based sheet comprising inorganic powder.
Patent Document 3 describes a PTP covering material film having a press-through property by providing innumerable scratch marks on a plastic film surface that do not penetrate, and a PTP covering material film having a protective layer formed by resin coating to protect the scratch marks, as well as a PTP employing the same.
Patent Document 4 describes a film comprising a uniaxially stretched common resin such as ordinary polystyrene, and a PIP package in which the uniaxial stretching direction and the long axis direction of the opening are aligned.